#121  
Old 12-22-2017, 11:11 AM
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A couple more comments:

The RACE 4575-AAA Dominators only had 2 corner idle on the Primary Metering Block.
The secondary metering block was like a early 3310 4 bbl (780 cfm carb) and the metering block was not machined for a power valve.
Racers assume minimal idle times and lots of WOT TIME. The early carbs were 1150 cfm.
A famous Ford Racer was 7 mph faster in speed vs the field with his 4575-AAA carb.

Tom V.

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  #122  
Old 12-22-2017, 01:49 PM
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Merry Christmas Tom...thanks

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466 Mike Voycey shortblock, 310cfm SD KRE heads, SD "OF 2.0 cam", torker 2
373 gears 3200 Continental Convertor
best et 10.679/127.5/1.533 60ft
308 gears best et 10.76/125.64/1.5471
  #123  
Old 12-22-2017, 05:11 PM
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Same to you, Thanks.

More on Holley Carbs after the Holidays.
Tom V.

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  #124  
Old 12-23-2017, 11:16 AM
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Was thinking about the Linkage on the early and later Holley Dominators.

At one time Holley sold a steel plate that was installed under the Dominator carbs so that if (for any reason) the internal secondary linkage came apart it would not go down into the intake/engine head ports.

They built that linkage in a couple of ways on the cam profile. The cam profile (inside the Dominator, see pic #1) somewhat resembled the cam profile on a 660 center squirter carb except it was much smaller in size.

It was held on the throttle shafts by a "Allen Head" threaded bolt (see Pic) . Royal PIA to mess with by a newby messing with carbs.

So that linkage came in three versions:
1 to 1 (all the blades move at the same rate)
Progressive (Similar to the 660 style cam profile)
Soft Progressive (similar to the racer modded 660 style cam profile with a custom opening rate.

Except on a Tunnel Ram type intake designed for Individual Runner applications (Doug Nash IR Intake, no reason to run that linkage.)
Because the carbs might be rated at 1050 cfm each (call it 1000 cfm per carb for easy math) Each IR runner would see a max airflow of 500 cfm. Wham, here comes the 500 cfm of air, then back to sleep, Wham, here comes the 500 cfm of air), then back to sleep, over and over. just like a Weber set-up on a SB Chebby with 48 mm Down Draft Carbs mounted.

Even with the Progressive and soft progressive internal linkage in the Dominators, it was not a full range type of set-up.
Ok for drag racing but not so good on a street car,

The external Dominator linkage is a much better linkage in my opinion, Kind of like a Tri-Power linkage but only two carbs involved (instead of three carbs).

A much better system

I have provided a couple of pics showing internal vs external linkage.

Tom V. Happy Holidays (Snowing in Michigan)
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Last edited by Tom Vaught; 12-23-2017 at 11:21 AM.
  #125  
Old 12-24-2017, 10:50 AM
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Christmas Eve, so not going to post on the Carb info today and just say:

Merry Christmas to the 3,000 + people who viewed this thread of Holley Information.

Tom Vaught

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  #126  
Old 12-24-2017, 09:16 PM
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Appreciate the kind words Tom, as mentioned though if not for the knowledge and information so freely offered here, I would have remained illiterate on the matter.

Thank You, from myself, as well as everyone who has, and will benefit.
........................................ ......
To a gift, that will truly keep on giving!


Merry Christmas

Frank

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  #127  
Old 12-26-2017, 09:10 AM
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Going to slowly get back up to speed on the posts by starting with a short one this morning, Hope everyone had a great Christmas Holiday.

Today I will talk a bit about the emulsion circuit (in general) and the high location IFR (Idle Feed Restriction) vs the historical low location IFR (Idle Feed Restriction).

The picture I have posted shows a "5 hole" Emulsion design, a upper Idle Feed Restriction, a lower Idle Feed restriction (Historical position) and the Angle Channel for the Main Metering Circuit.

1) The picture suggests:
a) Open up the Angle Channel to .160" drill size.
(This adds more fuel flow capability to the carb boosters, as easier to pull fuel thru a larger channel quickly.)

b) Drill out or unscrew the Holley "Upper Idle Feed Restriction". This will allow the reversal back to the "Lower Idle Feed Restriction" location. That mod was ALWAYS a bad idea.

c) Install a new "Lower Idle Feed Restriction" like the Holleys had for many years that worked great. Lots of idle instability with the High Mount Position IFRs.

The HP Metering Block shows the 5 Hole Emulsion capability which works ok with vast amounts of Dyno time on a NASCAR High RPM Race Mode vs Yellow Flag Fuel Economy Parade Lap Mode calibration.

Most tuners block the #2 and the #4 Emulsion Holes on Drag Race type carbs. Some even block the bottom #5 hole. Some think that it helps at the very top of the MPH curve. Most would see little benefit vs the old 3310 and 4781 List Number TWO HOLE Emulsion Circuit with calibrated holes at the #1 and #3 positions.

So the HP Metering Blocks can be FIXED if you spend time putting them back to what the old metering blocks Emulsions positions were and move the IFR back to the lower position. JMARKAUTO, TUNER, Shaker455, (All excellent Tuners), Myself, and others do this "reverse mod" often.

Unless you have access to a lot of Dyno Time don't mess with the Emulsion Circuit and instead just use the design from Holley had for years that worked very well on the Older carbs.

Tom V.
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  #128  
Old 12-26-2017, 05:14 PM
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Today I am posting an article written by a Magazine guy who does a lot better job on this carb article vs the previous article I posted.
(The one comparing his article vs the Racing Junk writers article).

New article:
http://www.hotrod.com/articles/ccrp-...-basics-guide/

I posted this article for three reasons:

1) The 1st and 2nd pics in the article show the expanded section of the main boosters at the bottom of the boosters. This tells me right off the picture is of a 750 Dominator carb with boosters that restrict the air flow thru the carb.
Remove those boosters and install new Dominator normal annular boosters and you have a 1050 cfm carb that just need to be recalibrated. Worth looking for those carbs at swap meets.

The third picture shows a internal brass emulsion tube that is inserted into the metering block to provide additional emulsion of the fuel to the carb. Mostly used in older Holley production carbs. The newer carbs removed that feature.

If I tried to explain that part without the picture provided it would be a very touch task.
'A Picture is worth 1000 Words" they say. Quote from Article: Unless you already know all about Holley metering idiosyncrasies, these emulsion circuits should be left to professional tuners. Just so you know, the basic function follows that increasing the size of these emulsion holes will reduce fuel flow and lean out the overall fuel curve."

Have a great day.

Tom V.

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  #129  
Old 12-26-2017, 10:28 PM
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Quoted from Car Craft magazine July 2005
"In a time not long past there was that guy down the street from you – that special car-crafting guru who could tune an engine by ear. He was revered by the local gearheads for his uncanny knack for creating not just impressive power, but also transforming chugging street slugs into razor-sharp sweetheart engines. He was like the Pinball Wizard – the deaf, dumb, and blind kid who could play those flipper fingers like he was part of the machine. We were all in awe of the Carb Wizard. While that guy still exists, we’ve discovered a little piece of electronic technology that can turn almost any knowledgeable car crafter in a Carb Wizard. This latest development in hand held electronic-power knowledge is the affordable air/fuel-ratio meter."

We are fortunate to have several Carb Wizards on the PY Board: Jon Hargrove, Shaker455, Cliff Ruggles, and for a while we had the CSU Carb Guys.

At Holley and later Ford, We used Air Fuel Meters similar to the Horiba MEXA-730λ units $$$$ for our Holley Carb work (but much earlier versions and very expensive). I think I still have one stored away somewhere.

So today December 2017, there are very good units out there that can do most of the stuff that the old units did and can do it very well.

If you really want to get into carb tuning, you really need that piece of Air/Fuel equipment.

You can buy what you can afford but you really need something.

So earlier today, I showed you a picture of a Emulsion Tube that was installed in a Holley carb.
When you get into high power applications that part does not need to be there.

Tuner will tell a story about Dominator carbs (with the main jets completely removed) and the fuel flow past that emulsion tube in the main well was equivalent to a 100 carb jet.

The emulsion tube blocked any additional flow thru the circuit even with the jets completely removed.
So I am not a fan of three circuit Dominator carbs at all. Just me, do what you want to do, guys.

More on carbs tomorrow.

Tom V.

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Last edited by Tom Vaught; 12-26-2017 at 10:34 PM.
  #130  
Old 12-27-2017, 08:57 AM
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Good Morning, Today I want to share some info I found in one of my excel files related to Holley carburetors. The info originally came from a closed down website called Motorsport Village.
Tuner, JMARKAUDIO, myself, and others used to post on that site. There was a lot of good Holley Carburetor Discussion there, BUT the owner of the site got tired of the BS and shut it down.

I had copied off a bunch of pictures and words of posts I made (as well as good pictures from others. Pictures was a strong point on that site.

So we have been talking about Dominator Carbs and other carbs with Emulsion circuits. I posted a picture of a Internal Emulsion Tube part made by Holley for some metering blocks.

So today I will provide a picture of a way to easily tell a metering block with that Emulsion part installed in it. I will call that pic "Wrong Block". I will also post a pic of a "Good Metering Block.

It will be easy to compare the two and avoid the "Wrong Block" parts.

I will also provide a picture of a normal (pre HP series) 2 hole Emulsion Block, a picture of the Kill bleed in the block, a picture of the Idle Feed Restriction, and a picture of the Power Valve Channel Restriction. So I will do this in several short posts. Tom V

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  #131  
Old 12-27-2017, 08:59 AM
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Good Metering Block vs Wrong Metering Block.

The good metering block (1st Picture) has 4 openings on the top of the block.
It uses "Cup Plugs" to seal the drilled passages in the block. Two Cup Plugs are
shallow plugs (close to the top of the block) and are for the Idle Circuit.
Two other plugs are recessed into the metering block and are for the Main Circuit.

The bad "Wrong" metering block (2nd Picture) has 4 openings on the top of the block.
It uses "Cup Plugs" and "Emulsion Tubes" to seal the drilled passages in the block.
Two Cup Plugs are shallow plugs (close to the top of the block) and are for the Idle Circuit.
Two other plugs are even with the Metering Block top surface and are for the Main Circuit.
Avoid using the "Wrong" Metering Block design blocks if possible. You CAN swap a "Good
Metering Block" on most carbs where a "Wrong" Metering Block was previously.

Tom V.
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Last edited by Tom Vaught; 12-27-2017 at 09:14 AM.
  #132  
Old 12-27-2017, 09:19 AM
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The next 4 pictures will help in identifying 4 "Control Orifices" found in all Good Holley Metering Blocks.

1) The Idle Feed Restriction
2) The Kill Bleed"
3) The Emulsion Holes
4) The Power Valve Channel Restrictions

A Pointer (attached to a hand) shows each restriction.

The Idle Feed Restrictions typically have a .030" to .040" restriction with most performance blocks being in the .036"
or .038" restriction size.

The Kill Bleed is typically a .026" restriction and its purpose is to stop syphoning of the fuel when the circuit is no longer active.

The Emulsion Holes are typically .026" to .028" with .028" being the most used size. The Good Metering Block for many years
only needed two Emulsion Hole restrictions to the Main Well. Then some hotrodders added a third hole neer the bottom of the
Emulsion Channel. And before you knew it we had 4 hole and 5 hole emulsion hole metering blocks (typically with only two or
3 holes actually used). I helped a FORD NASCAR team years ago with a carb set up for WOT racing and Caution Lap F.E. and
we had 10 Emulsion Holes in the custom metering blocks and dual Emulsion Channels. But it worked well for THAT APPLICATION.
Worthless expense on a typical carb.

The Last Picture is of the Power Valve Channel Restrictions. They can be in the .059" to .067" hole size with 850 CFM carbs using
the smaller PVCRs (.059") and larger jets. Lower CFM carbs = Larger PVCRs and smaller jets.

This concludes my info for the morning on Holley Carbs.

Tom V.
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Last edited by Tom Vaught; 12-27-2017 at 09:32 AM.
  #133  
Old 12-27-2017, 02:52 PM
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"Engineers do stuff for reasons"

This afternoon and maybe tomorrow will post up some info I posted on the Motorsport Village Website years ago.
They actually gave me credit for the info.

Info is from Tom Vaught, former Holley employee.

1) Why the Holley Hex Nut above the the Float Bowl has 6 sides (vs say 8 sides):

The thread used on the needle and seat that screws into the top of the float bowl is a 3/8-32
thread. There are 32 threads per inch cut on the needle and seat where it goes into the bowl.
One full turn of the Hex Nut will move the needle and seat 1/32” or .03125”
or for easy math about .030” upward or downward.

2) What the actual float movement is vs the tip of the needle (away from the seat):

The float has a 6 to 1 multiplication ratio so you turn the needle and seat hex nut one full turn downward, the float movement will be .03126 X 6 or .1875” lower in the float bowl and the average fuel level in the bowl will be for easy math .180” lower. Two “Flats on the Hex nut works out to about a 1/16” of fuel level change in the float bowl. If you keep accurate records of your float level position you can track the air/fuel ratio change (with an accurate air/fuel meter and get the fuel bowl fuel level vs the mail well fuel level dialed right in for your intake manifold/ carburetor/ engine installation angle dialed right in for best fuel control.

3) Why the fuel level rises in the bowl, (above the Holley Calibration Level), when a higher fuel pressure (vs the Holley fuel pressure spec of 6 psi) is used:

When the needle and seat (.110” size) is used with a factory float bowl and at the Holley fuel pressure calibration point (6 psi), the average float level height will be close to the “design fuel level” in the bowl and and the carburetor will will meter fuel properly. In some of the old Holley Books they used to show an external gage mounted on the fuel bowl to check fuel level before the “Sight Plug” type bowls were designed. If you add extra fuel pressure to the fuel line going to the bowl the needle and seat will have a higher pressure acting on the tip of the needle and seat. A small change here in force acting on the tip of the needle vs a fixed float buoyancy force X a 6 to 1 float ratio mentioned above means that the FUEL LEVEL IN THE BOWL WILL RISE TO A NEW AVERAGE LEVEL WITH INCREASED FUEL PRESSURE.

4) Why the fuel level rises in the bowl, (above the Holley Calibration Level), when a larger needle and seat is used (vs the Holley .110 needle and seat).

In the previous paragraph 3), the fuel level went up because the pressure on the float was higher due to the fuel pressure.
The other way the level can go up is by using a larger area needle and seat which also imparts more force against the float,
(raising the average fuel level.

A Holley 6-504 part Number is Holley's standard .110” Viton Needle and seat assembly
A 6-505 needle and seat will flow about 170-180 lbs of fuel per hour at 7 psi (depending on the specific gravity of the fuel used).
175 x 2 = 350 lbs of fuel per hour. About 630 horsepower if assuming a .55 lbs/horsepower/hr.

Using the larger needles and seats naturally will move more fuel BUT fuel level changes in the bowl will have to be monitored for
each combination vs expected air/fuel ratio and driveability.

5) Why “Float Drop” is important:
If you have the wrong float drop, the float can “hang” against the needle as it rides on the “hump” on the float level. There are two needle and seat lower needle dimensions. One needle has a 2 cm lower diameter and the other one has a 4 cm diameter. Naturally the 4 cm diameter needle and seat will not “hang” as easily as the “footprint” (diameter) is twice as large. If the float “hangs” you will have open flow into the bowl with no fuel control and flooding, fuel coming out of the vents, and potential “hydra-locking” of the engine. As second issue with the wrong float settings is that the fuel level in the bowl could be too low and uncover the power valve on acceleration. Special power Valves can help eliminate this issue.

6) Why Floats collapse after a Carburetor Fire:

If you have a carburetor backfire, and the carburetor is burning inside the venturis, the main-body gets hot quickly. This heat transfers to the air in the carburetor heating it and the also to the parts around the air. The brass floats have air inside of them when they were made. The air in the float gets hot, expands, and trying to get out of the float. Many times there are very small places where the air can escape but fuel cannot get into the floats. As soon as the engine is restarted, the cold fuel enters the bowl, the float is still hot. The float cools rapidly vs the lost air inside the float. Because the air pressure outside is now higher vs the inside of the float the float collapses (just like it would under boost). Now you have a big problem. The black Nitrophyl floats do not suffer this problem therefore as we know are a better component to use in a boosted carburetor. At least now you can explain to your buddy why his float looks like Chit when he was not running any boost through the carb, LOL!

7) What the “Standard” Brass Float should weight vs what the Black Nitrophyl Float weighs:

A Brass float weighs around 15 grams. (An average paper clip weighs 3 grams). The black nitrophyl float weighs about 11 grams. When you cut notches in the black float to allow for jet extensions, (or if you buy a black float with the notches already there), you should check the weight of the float on a gram scale to see if it is close to the right factory weight. You never know how much epoxy the guy used sealing the float, how deep he made the cuts, etc. Some floats for the road race guys and NASCAR guys are heavily modified. If the float is too light, (less than 11 grams stock, or if you want to make the float the same weight as the brass float you can add extra lead shot to get up to the brass float weight of 15 grams.

More on this tomorrow. I actually posted 16 pieces of info on the site. You got 7 today Part 2 tomorrow

Tom V.

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Last edited by Tom Vaught; 12-27-2017 at 03:02 PM.
  #134  
Old 12-27-2017, 08:17 PM
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Had a few minutes so going to post up the other pieces of info I wrote years ago.

8) Adding weight to a black float:
You drill a hole in the black float, add the weight, do a trial measurement on the gram scale, and when you are close you add the light coating of epoxy to seal the whole deal up. I am NOT a big fan of people making the black float weight the same as the brass float as the black float dimensions are different vs the brass float. The Brass float has a longer arm therefore more force on the needle and seat vs the Black float weight.

9) Lean Acceleration caused by an improper float level setting:

As was mentioned in 5), if the float level drops too low, the “head” that the fuel has to overcome in the main-well gets higher and the engine calibration goes lean. If the fuel level is too high, the “head” that the fuel has to overcome in the main-well, will be much less and the engine runs rich. There is a “sweet spot” that was designed into the carburetor fuel calibration over many years of testing vs the parts used and random “experimenting” will typically cause issues over time.
High pressure boosting is adding another level of knowledge to this carburetor database of proper settings.

10) Why Bowl Vent Clearance is important: (Spoke about this earlier in the sticky)

The vent whistle at the top of the metering block was added to prevent fuel slosh out of the carburetor bowl vents. A Rivet typically holes it in place. There may be a slight leakage around the vent but typically it is there for fuel control in the bowl. Trimming the vent is commonly done. You do not want the fuel to slam against the back wall of the carburetor under acceleration, climb the back wall, hit the roof of the bowl, move forward, and then enter the vent whistle. A whistle about 1.25' long typically works well. I trim the opening with an exacto knife to allow more area through the vent whistle too.


11) “Sight Plugs” Why they are different Front Bowl to Rear Bowl and why some people have carburetor problems when swapping out Holley Bowls for after-market fuel bowls:

Few Holley bowls today do not have a “Sight Plug” but the location of the sight plug can be in several different locations. Primary bowls will always have a higher sight plug location vs the secondary bowl location. The number varies all over the map. The average bowl difference will be around .220” difference with some going over .300” difference. Why is this important? Because the sight plug location sets where the “bottom of the threads” location is that everyone sets their fuel level to. As said earlier, you do not want to screw up the Holley Fuel Level Calibration Setting Point if you can help it.

12) “How to use a Primary Float Bowl on the Secondary side of a Holley carburetor:

IF you put a Primary bowl on the secondary side of a carburetor you can typically set the fuel level to the bottom of the threads deal and the LOWER the fuel level 4 FLATS.

13) Float Bowl Screws can be different:

A stock Holley Metering Block type bowl screw is 63mm long from the metal surface the screw gasket seals against to the end of the screw threads. About 2.48” long. The Metering Plate Holley screw is about 48mm long, about 1.89” long. You will notice that neither of the screws is the standard 2” long or 2.5” long hardware store bolts. At one time there were some screws out there that looked the same as the Holley typical parts but they were VERY CLOSE to the 2” and 2.5” length dimensions. You use one of these screws in your carb you are almost guaranteed that you will strip a thread in the main-body as the screw will bottom in the casting, have no where to go, and any additional tightening will pull threads.

14) Never use “Hot Rod” needles and seats parts vs the “Holley Design” needles and seats:

Above in #13 we had a screw length issues that could cause problems. In this line we have a needle and seat thread issue that needs to be addressed. Holley needles and seats ARE as mentioned above a 3/8-32 thread. Some of the “hot rod” old style needles and seats were a bastard thread then therefore would strip out the threads in the float bowl after installation in the bowl. USE ONLY HOLLEY DESIGN TYPE PARTS.

15) Differences between Holley needles and seats:

Holley used a few needle and seat designs over the years. Initially Holley had steel needles and later offered Viton tipped needles for many applications. Holley offered several orifice sizes, with the .110” needle and seat being the most common. Holley also changed the feed strategy to the needle. The old units used drilled holes in the upper and lower chambers (typically 4 holes). The later generation parts used a “Picture Window” rectangular shaped entry hole for more flow to the carburetor bowls. Today we have the stock type needles and seats and also “Bottom Feed” type racing needles and seats.

16) Viton tipped needles and seats vs steel needles and seats:

Last but not least Viton Tipped needles and seats vs steel needles and seats. The Viton stuff seals very well unless you get metal chips stuck in the viton tip. A steel needle and seat will typically allow the trash if small enough to pass through the needle and seat to the bowl. Steel needles and seats are used on higher performance applications when using exotic fuel blends as the viton tip parts are designed for normal pump fuels and some racing fuels. Most alcohol carbs will use a steel needle and seat for two reasons: Increased orifice diameter required where the viton part is not offered and durability from the corrosive fuel.
The increased fuel orifice diameter requirement can be corrected bu the dual needle and seat strategy but the corrosive fuel issue is still there.

Tom Vaught

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Last edited by Tom Vaught; 12-27-2017 at 08:23 PM.
  #135  
Old 12-28-2017, 09:09 AM
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A bit more on Emulsion Circuits on Holley Carbs

A Old Holley Carb had (as I previously showed) a metering block with two emulsion holes on each side of the metering block.
(The newer carbs have 3 emulsion holes per side, 4 holes per side, and even 5 holes per side.)

First off You need to understand a couple of circuits on a carburetor the Booster Circuit and the Emulsion Circuit.

I earlier spoke about the Booster Circuit as having several options on a Holley carb:
Basic Straight Leg "Crossbar" Boosters, Down Leg Boosters, Stepped Downleg Boosters, and Annular Discharge Boosters.
A Booster just take a venturi signal to the Main Jet and makes the Main Jet Signal bigger. (An Amplifier of the Main Jet Fuel Circuit Signal).
Three big things control how well a Booster works:
1) The Booster Design: Annular, Down Leg, Aerosol, etc
2) What the entry and the exit of the Booster looks like and how well was it designed
3) Where the Booster is placed in relation to the carbs venturi or lack of a venturi (3-BBL)

That being said we move on to the Emulsion Circuit: I also spoke on that a bit earlier, too.

We used to have a Very Smart Carb Guy from "Down Under" (Australia) named Shrinker on the Motorsports Board who said several times:
"You really don't need Emulsion Circuits if you do your job right." (Have to agree somewhat on that deal).

I posted before about OLDER HOLLEY CARDS having two Emulsion Circuits. Then Holley did a 3 circuit, 4 circuit, 5 circuit.
There was a reason why they did that!

Shrinker's Words: "Emulsion is a correction for incorrect vacuum performance from a booster. It is also a correction for incorrect main jet design. Carburetors can, and are, quite successfully used without emulsion. However the carburetor must be specifically tuned to each engine more accurately if its a no emulsion design. Using a design with no emulsion is not a carby suitable for hotrodders. It takes a high level of machining accuracy and a lot of testing to achieve a desired result without emulsion. It is very easy to alter fuel curves etc with emulsion. Using emulsion is cheap, easy, bulk mass production techniques."

I have seen Governor Carbs on Medium Duty Trucks (and a limited rpm range on the main circuit) that only had ONE Emulsion Hole.
But as Shrinker posted "A Zero Emulsion Carb is not a carby suitable for hotrodders". Holley did stuff for a reason on Commercial Vehicles vs Hot Rods.

1) It is very easy to alter Fuel Curves with Emulsion Circuits. Getting it right takes tons of effort (as I mentioned on NASCAR Carbs).
2) Emulsion Holes are cheap to do to a metering block and gives Hot Rodders and people who later FIX Hot Rodders carbs something to do.
(Remember, I took "screwed up carbs" and many times put them BACK to Holley's Build Specs and they Worked Great again.)

In simple terms, Emulsion Holes create air bubbles that lower the fuel density, The lower density fuel "floats" above the normal fuel.
That causes the lower density fuel to have a higher fuel surface level than normal density fuel.

Once the fuel surface level is up to the height of the outlet tube it can flow to the booster. At that point the engine starts to run on the fuel.
At low air flow levels thats the physics behind the Emulsion Circuit. You are using air to make the surface of the fuel closer to the discharge outlet.

At higher flows through the carb the main jet restriction causes a reduction of the liquid level in the well and that lower level uncovers some Emulsion Hole Bleeds. When that happens, the air flow through the bleeds blows the fuel along its path. The amount of "blow thru" is controlled by the Main Air Bleed and the sizing of the various Emulsion Bleeds.

Under Acceleration, when the fuel flow into the bowl causes a lowering of the level (high fuel demand). The pressure on the entrance to the main jet is changed, so the flow rate of the jet is changed and that in turn changes the level of fuel in the main well.

You really have to be "on your game" to be successful when messing with Emulsion Jet changes.

More Later.

Tom V.

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Last edited by Tom Vaught; 12-28-2017 at 09:20 AM.
  #136  
Old 12-28-2017, 07:54 PM
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Well My post to list Actual Holley Accelerator Pump Cam data was a wasted 3 hours. The PY Computer would not allow me to edit the last batch of data before it locked me out of the edit screen.

Tom V.

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Old 12-29-2017, 07:25 AM
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Well I tried yesterday to give you the actual data that generated the Accelerator Pump Cam profiles
but that did not work out with the posting capabilities of the message boxes. So I am providing a link today to the PDF File generated by Holley. http://documents.holley.com/pumpcamgraph.pdf

Maybe that will work for you as you can still figure out the lift for a given grid location.


Tom V.

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  #138  
Old 12-29-2017, 09:08 AM
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Food for thought:

If you have a Dominator Carb that has the ability to get 12.6-12.8 Air Fuel ratio on a 2 circuit Dominator Carb, then why is a third circuit needed?

Basic Reason, To extend the t-slot circuit artificially.

A idle/t-slot is a very small orifice with a small Idle Air Bleed. The Main Air Bleed is small so it will not start the Main Booster flow early, but this can be done by using a 3 circuit carb.

The 3rd circuit is filling the fuel delivery space between the Idle Circuit and the Main Booster Circuit. From a Holley design point there might be some benefits to that extra complexity, (and some $$$), but from a reality stand point is it really necessary to have that third circuit Holley Dominator when a 2 circuit Dominator can do the same thing and it will be cheaper and easier to calibrate because it does not have that Emulsion tube inside the metering block (for the 3rd circuit).

Tom V.

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  #139  
Old 12-29-2017, 09:29 AM
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Great info Tom. And after all that, if your Holley doesn't play, toss it in the creek, and get a Q-JET.

I wasn't paying attention on the Front & Rear accel pump cams tuning.

Tom, To Tune or not to keep tuning; assuming plugs read well, starts, idles & runs seemingly normal and good, can you write a concise process to go through (in order) to assure (my) a 1050 is on a top-tune?

  #140  
Old 12-29-2017, 03:55 PM
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Don't blame the carb for a lack of tuning knowledge as far as Holley Carbs go, vs a Q-Jet, HIS.

At high speeds/rpm conditions, the carb will want to go rich or lean depending on the calibration and high speed air bleed configuration. You want the carb to "flat line" (maintain the same air/fuel ratio) at high rpm.

The only way to know that is by logging air/fuel ratio on the track at high speed and load.

Power Valves/ Power Valve Channel Restrictions are used on street carbs at high speed to hit that flat line condition along with high speed air bleeds. The trick is to know what the curve or flat line needws to look like before tuning.

Many just do the trial and error set-up or pay a carb guy to get it close and leave it alone. In both cases you waste money on gas trying to get it right. Listen to the air/fuel gage and the engine, as well as the track segment numbers:
60 ft, 330, 660, and 1320 times and top mph number.

All I can do for you guy. Your carb/ your engine/ your program, take ownership of it vs help me, help me, where you just write the check.

Tom V.

ps At High Speed/ High RPM you want the HORIZONTAL LINE shown on the right side of the picture/graph. The picture shows a curve which happens often.
You don't want too lean but you also do not want too rich at high speed 12.7 - 12.8 A/F is a good number to shoot for. The "Lean to be Mean" guys kill a lot of parts and this is for the average guy.
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Last edited by Tom Vaught; 12-29-2017 at 04:10 PM.
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